Sputum analysis involves microscopic examination of the cells that are either coughed up from the lungs, or are collected through a special instrument called a bronchoscope. Sputum analyses can diagnose at least 30% of lung cancers, some of which do not show up even on chest x rays. In addition, the test can help detect cancer in its very early stages, before it spreads to other regions. The sputum test does not, however, provide any information about the location of the tumor and must be followed by other tests, such as bronchoscopy, where machines can detect cancerous cells without the need to open the chest.
Lung biopsy is the most definitive diagnostic tool for cancer. It can be performed in several different ways. The doctor can perform a bronchoscopy, which involves the insertion of a slender, lighted tube, called a bronchoscope, down the patient's throat and into the lungs. In addition to viewing the passageways of the lungs, the doctor can use the bronchoscope to obtain samples of the lung tissue. In another procedure known as a needle biopsy, the location of the tumor first is identified using a CT scan or MRI. The doctor then inserts a needle through the chest wall and collects a sample of tissue from the tumor. In the third procedure, known as surgical biopsy, the chest wall is opened up and a part of the tumor, or all of it, is removed. A doctor who specializes in the study of diseased tissue (a pathologist) examines the tumor samples to identify the cancer's type and stage.
Mai Tran, Teresa G. Odle, The Gale Group Inc., Gale, Detroit,